Extra sleepy

Hi mamas, I'm in wk4 day3. I'm still attending school and working full time. I usually get about 7 hours of sleep and am not overly tired. I woke up around 8am today, went to school, and then lunch and target with a girlfriend after. By about 1:30 I was so tired. Like couldn't concentrate on anything tired. I came home and took a 90 minute nap. Is this normal for early pregnancy and does it last the majority of pregnancy?